Glass containers and other articles are often composed of so-called soda-lime glass, also called soda-lime-silica glass or “SLS” glass. The glass used to make such articles may be colored, for example, to provide the articles with various aesthetic or functional properties. Colored glass can be produced by introducing one or more colorants, e.g., metals or metal oxides, into the glass during its manufacture. Oftentimes, the added colorants will immediately impart color to the glass. But sometimes color may need to be developed in the glass by subjecting the formed glass articles to a heat-treatment process known as “striking.” This heat-treatment process may involve heating the glass articles to a temperature above their normal annealing temperature for a sufficient amount of time for the colorants in the glass to interact or “strike” and visibly change the color of the glass.
“Color” is an aspect of an object that can be described in terms of its hue, saturation, and value, and these properties of color can be used to distinguish differences in color. Thus, a “color change” or “change in color” occurs when the hue, saturation, and/or value of a color is changed. Such a change is “visible” if it can be detected by an average human viewer at an arm's length viewing distance or another convenient distance, without special viewing equipment. The term “coloration,” as used herein, means the overall visual appearance of an object or a portion of an object with regard to color.
A general object of the present disclosure, in accordance with one aspect of the disclosure, is to provide a process for heat-treating a glass container having a strikable glass container composition to impart coloration to the glass container. One or more portions of the container are selectively and locally exposed to a temperature at or above a glass container striking temperature to affect a color change in the one or more portions of the glass container. An apparatus is also provided that is configured out carry out such processes.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
A process for imparting coloration to a glass container in accordance with one aspect of the disclosure includes: (a) providing a glass container having a strikable glass container composition, and (b) exposing a selective portion of the glass container to a temperature at or above a glass container striking temperature for a time sufficient to affect a color change in at least the selective portion of the glass container. The selective portion of the glass container may be exposed to a temperature at or above a glass container striking temperature for a time sufficient to establish a temperature gradient in the glass container and to produce a gradient of color in the glass container. Step (b) may involve passing the glass container through an interior having a vertical temperature profile that includes a relatively hot zone and a relatively cool zone.
In accordance with another aspect of the disclosure, there is provided a process for imparting coloration to a glass container that includes: (a) providing a glass container having a strikable glass container composition, (b) introducing the glass container into an environment having a substantially uniform temperature, and (c) locally heating or cooling discrete portions of the glass container to affect a color change or to prevent a color change from occurring in the discrete portions of the glass container.
An apparatus for imparting coloration to a glass container in accordance with one aspect of the disclosure includes: an interior, a support to support a glass container within the interior, a heating system to locally heat a first region within the interior to a temperature at or above a glass container striking temperature, and a cooling system to locally cool a second region within the interior to a temperature below the glass container striking temperature. When a glass container having a strikable glass container composition is passed through the interior, a first portion of the glass container is selectively and locally heated to a temperature at or above the glass container striking temperature such that a color change is produced in the first portion of the glass container, and a second portion of the glass container is selectively and locally maintained at a temperature below the glass container striking temperature such that the second portion of the glass container does not change color when the glass container is passed through the interior.
In accordance with another aspect of the disclosure, there is provided an apparatus for imparting coloration to a glass container. The apparatus includes: an interior, a support to support a glass container within the interior, a plenum extending across the interior, and a manifold in fluid communication with an opening in the plenum. The manifold extends from the plenum at least partway into the interior and has one or more orifices through which a gaseous medium can flow between the plenum and the interior. Each orifice of the manifold is configured to direct a gaseous flow at a discrete portion of a glass container to affect a color change or to prevent a color change from occurring in the discrete portion of the glass container.